Electron beam devices, in particular scanning electron microscopes, are used for examining surfaces of objects (samples). For example in the case of a scanning electron microscope, an electron beam generated by a beam generator is focused by an objective lens for focusing onto the object to be examined. A deflector is used to direct the electron beam (subsequently also referred to as the primary electron beam) over the surface of the object to be examined, thereby scanning the surface. The electrons of the primary electron beam interact with the object in this process. As a result of this interaction, in particular electrons are emitted from the object (secondary electrons) or electrons of the primary electron beam are backscattered (backscattered electrons). Secondary and backscattered electrons form the secondary beam and are detected via a detector. The thus generated detector signal is used for image generation.
It is also known to equip a scanning electron microscope with an ion beam column. Ions used for preparing objects (e.g., polishing the object or depositing material on the object) or also for imaging are generated via an ion beam generator situated in the ion beam column. The applicant markets such a scanning electron microscope, which is available under the name “LEO CROSSBEAM”.
To achieve the greatest electron-optical resolution, the primary electron beam must be delivered perpendicular to the surface of the object to be examined. Vertical ion irradiation is also desirable to achieve uniform preparation of the object. FIG. 1 shows a system previously used by the applicant in a scanning electron microscope. Situated in the scanning electron microscope is an electron beam column 2, its beam axis 24 corresponding to the vertical line. An ion beam column 3 having a beam axis 25 is also provided. Beam axis 25 is tilted at an angle 2α with respect to beam axis 24. Beam axis 24 and beam axis 25 meet on a receiving surface 5 of an object slide 4 at a point of coincidence. To obtain the best electron-optical resolution or best preparation via the ion beam, object slide 4 is tilted in such a way that either beam axis 24 or beam axis 25 is perpendicular to receiving surface 5 of object slide 4.
Subsequently, object slide 4 must be tilted at an angle 2α to be moved from one position to another. This is a particularly large tilt angle. However, the greater the tilt angle, the less precise and error-prone the perpendicularity of receiving surface 5, i.e., the surface of the object to the ion beam or primary electron beam, in particular due to mechanical forces.
A tilting mechanism which also has these disadvantages is known from DE 196 08 082 A1. This publication relates to an ion beam preparation device for processing samples for electron microscopy. A preparation process is observed using a scanning electron microscope. The optical axis of the scanning electron microscope is aimed at a sample positioned in a sample holder. The known device also has an ion source aimed at the sample, the sample holder and the ion source being situated about the central rotational axis so that they are tiltable with respect to one another.
Accordingly, it is desirable to provide a particle beam device which makes it possible, using simple means, to align the object surface perpendicular to the beam axes of the particle beam columns in the most accurate and error-free manner possible.